1. Field of the Invention
The present invention relates to a mobile machine for rehabilitating a ballast bed supporting a track comprising two rails fastened to ties, each rail having a field side and a gage side, which comprises an elongated machine frame extending in a longitudinal direction and supported by spaced apart undercarriages on the track for mobility in an operating direction, and mounted on the machine frame between the undercarriages a vertically adjustable device for excavating ballast, a ballast discharge device arranged rearwardly of the ballast excavating device in the operating direction, the ballast discharge device having a discharge end, a track lifting device and a vertically adjustable ballast tamping head, the track lifting device comprising flanged rollers supporting the track lifting device on the track, and the ballast tamping head comprising reciprocable tamping tools for tamping the discharged ballast.
2. Description of the Prior Art
U.S. Pat. No. 5,172,636 discloses a ballast cleaning machine with an elongated, bridge-like machine frame whose opposite ends are supported on undercarriages running on a track. The ballast is excavated by an endless excavating chain running under the track centrally between the undercarriages, and the excavated ballast is transported by a conveyor arrangement to a ballast screening car which is coupled to the machine and precedes the same in the operating direction. A further conveyor arrangement transports the cleaned ballast from the ballast screening car rearwardly to a ballast discharge device located behind the excavating point, and the ballast discharge device has an elongated discharge conveyor associated with each track rail and pivotal in a horizontal plane. Ballast discharge chutes are affixed to a track lifting unit underneath the discharge ends of the discharge conveyors for distributing the cleaned ballast adjacent each rail. The track lifting unit is linked to the machine frame and has flanged rollers running on the track rails, and it is equipped with a vibrator for vibrating the track and the ballast discharged underneath it so that the ballast flow is improved. Two vertically adjustable ballast tamping heads are mounted on the machine frame rearwardly of the track lifting unit in the operating direction and their tamping tools are immersed in the shoulder ballast at opposite ends of the ties for shovelling the lowest layer of the shoulder ballast up to the area adjacent the tie ends where the ballast is compacted by pressing it under the ties. This machine is very long and, therefore, cannot be used under all track conditions.
U.S. Pat. No. 4,794,862 discloses a track leveling and ballast tamping machine equipped with means for delivering additional ballast for effective tamping. For this purpose, a ballast storage bin is mounted on a machine frame between the undercarriages supporting the same on the track, and the bin has outlet openings for discharging ballast into the cribs. A track lifting and lining unit as well as a tamping unit are mounted on guides on the machine frame rearwardly of the ballast outlet openings, and these units are longitudinally displaceable in unison so that the machine may be advanced continuously while tamping is effectuated intermittently. This machine is used in combination with a track renewal train or behind a ballast cleaning machine.
U.S. Pat. No. 4,479,439 discloses a machine arrangement for rehabilitating the subgrade of a track. The arrangement comprises a series of work vehicles which are coupled together, and each vehicle carries different operating tools. The ballast bed under a lifted track is removed by a ballast excavating chain and conveyed forwardly in the operating direction. A layer of sand is then laid on the exposed subgrade, planed and uniformly compacted. A ballast discharge device then lays a new ballast bed on the sand layer, and a satellite vehicle carrying a tamping unit may then tamp the new ballast bed. The tamping unit and the associated track lifting unit may be longitudinally displaceable on the machine frame of the satellite vehicle so that the tamping unit may be longitudinally displaced during tamping at the same rate of speed as the forward speed of the entire machine arrangement so that the arrangement may be advanced continuously. This machine arrangement is quite long and, therefore, its usefulness is limited.